The present invention relates to a disc brake for bicycle, and more particularly to a mechanical type disc brake in which a toggle mechanism cooperates with a pull bar to amplify a force applied to the toggle mechanism via the pull bar, so as to increase a tail braking force and avoid brake dragging.
A bicycle has developed from a conventional traffic means into a means useful in many specific fields. There are more and more people using bicycles in a variety of occasions. Functional requirements for a bicycle are much more strict than ever before, particularly a good brake system that involves the safety of riding the bicycle has drawn people""s high attention to it. Among different types of braking mechanisms for bicycles, there is a rim brake that is also referred to as a V-type brake. The rim brake gradually fails to satisfy the current requirements for safety in riding a bicycle, particularly a cross-country or a mountain-climbing bicycle. For a bicycle to maintain an absolutely safe braking performance and a highly sensitive mobility under very bad weather and riding environments, it is necessary to develop a new braking mechanism for bicycle to satisfy the strict requirements. A mechanical-type disk brake has gradually drawn people""s attention because it has been tested and proven to be safer and more comfortable for use than the V-type brake.
U.S. Pat. No. 3,878,921 discloses a brake system for bicycle, and U.S. Pat. No. 3,927,736 discloses a disk brake for bicycle, both of which have considerably simple structures that enable easy production and assembly thereof. However, these types of brake systems for bicycle all are subjected to a locked brake due to an overly high friction among components thereof and are therefore very dangerous to bicycle riders and need further improvements. Another problem with the conventional mechanical-type disk brake for bicycle is a weak tail braking force that could not be effectively enhanced up to date.
U.S. Pat. No. 3,997,033 discloses a disk brake mechanism that has the advantages of simple structure, easy to assemble, and smoothly developed braking force. However, this type of disk brake does not have the effect of amplifying the braking force to result in an insufficient braking force, and does not have proper restoring means to result in delayed return of brake shoes. That is, this type of disk brake is less sensitive.
In addition, the steel cable employed in general mechanical-type disk brake, as being limited by a tension thereof, prevents the conventional mechanical-type disk brake for bicycle from having an enhanced tail braking force.
It is therefore tried by the inventor to develop a new mechanical-type disk brake for bicycle to eliminate the above-mentioned disadvantages.
A primary object of the present invention is to provide a mechanical type disc brake for bicycle to effectively increase the braking force, provide an ideal brake curve, and prevent a brake dragging due to an overly large frictional force between the brake linings and the brake discs.
To achieve the above object, the present invention mainly includes a housing, a mounting bracket for connecting the housing to a fork of the bicycle, a pull bar pivotally connected to an outer side of the housing, an actuating rod extended into the housing via the pull bar, and a toggle mechanism, sliders, brake linings, and a restoring element separately mounted in a locating space in the house at predetermined positions. When the pull bar is pulled to cause the actuating rod to vertically act on the toggle mechanism, two actuating blocks of the toggle mechanism are moved outward to push against the sliders and the brake linings to create a brake effect. Contact surfaces between the actuating blocks of the toggle mechanism and the sliders are cambered surfaces to avoid an overly large frictional force between the brake linings and brake discs that would result in a brake dragging.
Another object of the present invention is to provide a mechanical type disc brake for bicycle that employs the principle of leverage to amplified a force applied to brake the bicycle, so that the bicycle always has good brake performance under different riding environments, and the problem of weak tail braking force often occurred in general mechanical type disc brake can be solved.
A further object of the present invention is to provide a mechanical type disc brake for bicycle that includes restoring means for an actuating rod and brake linings thereof to actually return their initial positions after a braking force is removed, so that the disc brake can be more accurately controlled.